Endothelial cell cultures, established from bovine umbilical cord arteries and subsequently infected with Cowdria ruminantium, were used as antigen in the indirect fluorescent antibody test. Bovine sera (374) and caprine sera (388) collected in 6 provinces of Mozambique were tested. Overall, 30.4% of goat sera had antibodies to Cowdria, and 43% of sera collected from cattle. North of the River Save, where the tick Amblyomma variegatum is highly prevalent, overall percentages of positive sera were low, 10% in goats and 20% in cattle. However, south of the river where the tick Amblyomma hebraeum is abundant percentages were much higher, 63.5% in goats and 59.4% in cattle. These results are discussed in relation to field observations that clinical disease is rare or absent in the north with enzootic instability in goats and Friesian calves in the south.